Say it ain’t so! Is Hollywood’s greatest power friendship over between Rihanna and Katy Perry? It looks like it might be according to several sources. The duo are said to be on the outs after Perry and Rihanna had a disagreement over Chris Brown’s involvement in Rihanna’s life.

The two music stars, who are both known for being provocatively outspoken, are in a battle over Brown, who physically abused Rihanna during a fight in 2008. The “Fireworks” singer thinks Rihanna is “making a huge mistake” by entertaining the idea of rekindling a relationship with her violent ex Chris Brown.

According to a source from Katy’s camp, “They’re barely talking and ever since the couple reunited, there has been tension between them. Katy has been spending a lot of time with pals Robert Pattinson and Kristen Stewart. Katy fears Rihanna is making a huge mistake and doesn’t want to be part of it.”

Back in September, Rihanna and Katy Perry were publicly seen sitting next to each other at the MTV Video Music awards, where the two nuzzled, exchanged smiles, and whispered probably sarcastic nothings over the snooze-fest of the award show. However, since Chris Brown and Rihanna have reunited the friendship has been strained.

Ironically enough, the first indication of Rihanna reuniting with Chris was during the same award shows, where the two were pictured sharing a kiss right before Brown collected his award.

The most telling sign of Katy Perry and Rihanna calling it quits as best friends is the absence of Katy Perry, who was missing from Rihanna’s Halloween party. Rihanna had also failed to show her face at Katy’s birthday party as well. This is from someone who once took the reigns on throwing Perry her very own bachelorette party before Perry married comedian Russell Brand.

Do you think there’s a secret rift between Katy Perry and Rihanna? Who do you side with?